Small-Mouthed Salamander Ambystoma texanum

Adult from Decatur County

Identification

These are fairly large, gray or black salamanders with lighter gray mottling on the sides. Small-Mouthed Salamanders are morphologically identical to Streamside Salamanders, but the two can usually be distinguished by range and habitat. Small-Mouthed Salamanders have a distinctively short head which serves well in distinguishing them from other species in the family Ambystomatidae. Adult Small-Mouthed Salamanders can grow to be 5-7 inches in total length. Small-Mouthed Salamanders lay eggs either individually or in small jelly-like masses in a slightly elongated shape. They are attached to vegetation or debris in shallow water. Larvae are brownish with lighter saddles and grow darker with age. Older individuals also possess a light lateral stripe, and they transform at around 2 inches in total length.

Eggs from Marion County
Young larva from Marion County
Juvenile from Marion County

With the exception of some minor differences in tooth and bone structure that are not easily seen, the Streamside Salamander (Ambystoma barbouri) is morphologically identical to this species. A notable difference between these species is their reproductive natural histories. While the Small-Mouthed Salamander tends to favor pools and ponds and lays eggs in smaller clumps attached to vegetation, the Streamside Salamander breeds primarily in streams and attaches large egg masses to the underside of submerged rocks and logs. The only region in which the two species could potentially be sympatric (occurring side-by-side) is in southeastern Indiana--especially parts of Jefferson, Jennings, Decatur, Clark, Scott, and Floyd Counties. Flat, seasonally wet uplands and floodplains are the most likely types of habitats in which the species would be indistinguishable without genetic confirmation, because the sluggish streams of the region could provide adequate breeding habitat for either species. The Jefferson's Salamander (Ambystoma jeffersonianum) and the Blue-Spotted Salamander (Ambystoma laterale) both co-occur with this species throughout southern and northern Indiana, respectively, and are similar in appearance. Both species tend to have more blue or gray speckling as opposed to the lichenate coloration that is typical in this species, and both species are generally more slender with elongated snouts. Further complicating the matter are the unisexual Ambystoma, which sometimes have genomes derived in part from the Small-Mouthed Salamanders. These unisexual salamanders are most common in northern and central Indiana. In Posey County, the Mole Salamander (Ambystoma talpoideum) utilizes the same lowland habitat as this species, but it is a more robust salamander with a proportionately larger head and smaller tail.

Ecology and Conservation

Forested bottomlands and floodplains are the most common habitat types in which this species is found in Indiana though flat, marshy uplands are also occupied throughout the central part of the state. Open marshes and wet fields are also inhabited provided burrows are readily available. Crayfish burrows are likely very important for this species in many areas, although small mammal burrows may also be used. Small-Mouthed Salamanders are most active during their winter and early spring breeding season, but mild rainy weather at any time of the year can prompt them to become more surface-active. They commonly inhabit crayfish burrows, but are found under cover at the surface during rainy weather. They remain underground throughout dry periods and are seldom seen during the summer. Larval Small-Mouthed Salamanders feed initially on small zooplankton and move on later to larger prey. Adults feed on a variety of invertebrates, especially earthworms. Cannibalism has been noted in this species.

Cattail marsh from Wayne County
Seasonally wet marsh from Marion County
Cattail marsh from Marion County

Small-Mouthed Salamanders breed in shallow, ephemeral waters and will often utilize pools or ditches off of large wetlands rather than breed in the larger body of water. They deposit eggs in small clumps to vegetation, sticks, and other debris. Their breeding activity is stimulated by mild temperatures and rainy weather occurring any time from December through March (or February through April in the northern part of their range). They typically metamorphose from early-mid summer.

This species is common throughout its range and seems to adapt well to human-altered environments provided there are seasonally wet, low areas and burrows. No major threats to this species conservation in Indiana are currently known.

Distribution

This species is found throughout the central United States from southeastern Michigan to Alabama in the east, and central Texas into southeastern Nebraska and Iowa in the west.

Small-Mouthed Salamanders range almost statewide in Indiana, but are found mainly in flat, seasonally wet habitat. They are notably absent from the Switzerland Hills of southeastern Indiana, the majority of the unglaciated hills of south-central Indiana, and the majority of the northernmost counties in the state.

Taxonomy

The Small-Mouthed Salamander (Ambystoma texanum) has no recognized subspecies. It belongs to the family Ambystomatidae, which is represented in Indiana by eight species (plus the unisexual Ambystoma)--the most of any state!

Literature Cited

Brodman, R. 2003. Amphibians and Reptiles from Twenty-three Counties of Indiana. Proceedings of the Indiana Academy of Science 112:43-54.

Conant, R. and J. T . Collins. 1998. Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin, New York, NY.

Klueh-Mundy, S and J. Mirtl. 2014. Ambystoma texanum. Small-mouthed Salamander. Geographic distribution (Lawrence County). Herpetological Review 45:273.

Minton, S. A. Jr. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science, Indianapolis, IN.

Petranka, J. W. 1998. Salamanders of the United States and Canada. Smithsonian Institute Press, Washington D.C.

Distribution Map
Distribution map of Small-Mouthed Salamander (Ambystoma texanum)
Photographs